This project concerns a characterization of enzyme repression in bacteria, and particularly the repression of arginine biosynthetic enzymes in Escherichia coli. The research will focus on aspects of the molecular mechanism underlying repression. The emphasis will be on the sites and mode of repressor action and on the nature of the repressive complex. Both the translational and the transcriptional components of represson will be studied. The work is to include an examination of repressor-ribosome interactions.